They offer multiple services with their uptime monitor which is very helpful to identify issues in our site within seconds of them happening! The price can be expensive for some small businesses depending upon how many users they have or what type of traffic you receive each month.
We've been able use this tool since we started using it now several years ago so there isn't much more I would like as far as features goes but if those few things were fixed then that'd make me happier too!! It's helped us out alot by giving immediate feedback regarding any downtime experienced through my business' websites - especially during peak usage times such as new months where demand increases greatly (not just at Christmas time).